Systems and methods for current sensing

ABSTRACT

Systems and methods described herein are directed towards differential current sensing a current sensor having two or more magnetic field sensing elements that are oriented to sense a magnetic field generated by a current through an external conductor in the same direction. The current sensor can be positioned such that at least one first magnetic field sensing element is vertically aligned with the external conductor and at least one second magnetic field sensing element is not vertically aligned with the external conductor. The magnetic field sensing elements may be spaced from each to measure a gradient field and can generate a magnetic field signal indicative of a distance between the respective magnetic field sensing element and the current carrying external conductor. A difference between the magnetic field signals can be determined that is indicative of the current through the external conductor.

BACKGROUND

Some conventional electrical current sensors are positioned near acurrent-carrying conductor to sense a magnetic field generated by thecurrent through the conductor. The current sensor generates an outputsignal having a magnitude proportional to the magnetic field induced bythe current through the conductor.

The accuracy with which a magnetic field-based current sensor senses anintended current can be affected by its immunity to stray magneticfields. Some conventional current sensors employ shields, sometimes inthe form of a ferrite or other magnetic core positioned around theconductor, to concentrate the magnetic field in the vicinity of thesensor and to thereby provide a level of shielding against stray fields,such as those that may be caused by currents flowing in adjacentconductors.

SUMMARY

Systems and methods described herein are directed towards currentsensing by a current sensor having two or more magnetic field sensingelements that are oriented to sense a magnetic field generated by acurrent through an external conductor in the same direction. Each of thetwo or more magnetic field sensing elements can generate a magneticfield signal indicative of a distance between the respective magneticfield sensing element and the current carrying conductor. In someembodiments, the outputs of the magnetic field sensing elements can besubtracted to differentially measure the magnetic field generated by thecurrent through the conductor. Thus, a difference signal correspondingto the difference between the magnetic field signals can be generatedthat rejects stray fields and is indicative of the current through theconductor.

The current sensing can be performed by positioning the current sensorover an edge (e.g., straddling the edge) of the conductor such that atleast one first magnetic field sensing element is over or otherwisevertically aligned with the conductor and at least one second magneticfield sensing element is not over or otherwise vertically aligned withthe conductor. The magnetic field sensing elements may be spaced fromeach to measure a gradient. Thus, the spacing may be selected based on adesired gradient (e.g., largest gradient) and/or a level of the currentthrough the conductor.

The current sensor may be provided in a package having a lead frame thatallows for high isolation between the conductor and the output signallead(s) of the sensor. For example, the current sensor can include oneor more substrates (e.g., semiconductor substrates) that support themagnetic field sensing elements and the lead frame can include a dieattach paddle and a plurality of leads. The one or more substrates canbe attached to the die attach paddle. In an embodiment, a firstplurality of leads adjacent to a first side of the die attach paddle canbe coupled to the die attach paddle and a second plurality of leadsadjacent to a second side of the die attach paddle can be spaced fromthe die attach paddle. With this arrangement, one set of leads can becoupled to a non-current carrying surface adjacent to the conductor andthe second set of leads can be coupled to the current carrying conductorbut spaced from the die attach paddle. With the second set of leadsspaced from (i.e., not in contact with) the die attach paddle, highisolation from the conductor is achieved. The spacing between the secondset of leads and the die attach paddle may be selected based at least inpart on a level of the current, a voltage of the conductor, andisolation requirements. It should be appreciated that in the currentsensor arrangements described herein, the conductor can be isolated fromthe one or more substrates and the first plurality of leads through avariety of different techniques. For example, in some embodiments, toprovide voltage isolation, the die attach paddle can be coupled to thesecond plurality of leads. However, an isolation layer (e.g., tape,non-conductive die attach paddle) can be disposed between the one ormore substrates and the die attach paddle and one or more wire bonds canbe coupled from the one or more substrates to the signal leads.

The conductor may be referred to herein as an external conductor as thecurrent sensor is disposed over or otherwise adjacent to the conductorand the current does not flow through the current sensor package. Forexample, in some embodiments, the current sensor may be positioned suchthat it hovers over the edge of the external conductor.

A downset configuration of the die attach paddle may be provided suchthat at least some of the plurality of leads are positioned at differentheights than the die attach paddle (and thus substrate and magneticfield sensing elements) relative to the conductor to bring the dieattach paddle closer to the conductor than otherwise possible. Forexample, the plurality of leads can be disposed at a first height withrespect to the conductor and the die attach paddle can be disposed at asecond height with respect to the conductor. The first height can begreater than the second height such that the die attach paddle,substrate and plurality of magnetic field sensing elements are disposedat a lower height and in a closer proximity to the current carryingconductor, than otherwise possible.

In a first aspect, a current sensor for sensing a magnetic fieldgenerated by a current through an external conductor comprises a leadframe having a first surface and a second, opposing surface, the leadframe comprising a die attach paddle and a plurality of leads, one ormore substrates attached to the die attach paddle and a plurality ofmagnetic field sensing elements supported by the one or more substrates.At least one first magnetic field sensing element of the plurality ofmagnetic field sensing elements is spaced from at least one secondmagnetic field sensing element of the plurality of magnetic fieldsensing elements and the at least one first magnetic field sensingelement and the at least one second magnetic field sensing element areorientated to sense the magnetic field in the same direction. The atleast one first magnetic field sensing element is configured to generatea first magnetic field signal indicative of a distance between the atleast one first magnetic field sensing element and the conductor andwherein the at least one second magnetic field sensing element isconfigured to generate a second magnetic field signal indicative of adistance between the at least one second magnetic field sensing elementand the conductor. The current sensor further comprises a circuitresponsive to the first magnetic field signal and to the second magneticfield signal and configured to generate a difference signal indicativeof a difference between the first magnetic field signal and the secondmagnetic field signal. The difference is indicative of the currentcarried by the conductor. For example, the first and second magneticfield signals can be proportional to the current carried by theconductor and that the proportionality constant can be indicative of thedistance between the respective magnetic field sensing elements.

In some embodiments, the one or more substrates may have a first surfaceattached to the die attach paddle and a second, opposing surface, andthe plurality of magnetic field sensing elements can be supported by thesecond surface of the one or more substrates. In other embodiments, theone or more substrates may have a first surface attached to the dieattach paddle and proximate to the lead frame, and a second, opposingsurface distal from the lead frame and the plurality of magnetic fieldsensing elements can be supported by the first surface of the one ormore substrates.

The at least one first magnetic field sensing element can be verticallyaligned with the external conductor and the at least one second magneticfield sensing element can be positioned such that it is not verticallyaligned with the external conductor. The die attach paddle may compriseone or more slits, slots or apertures. The one or more slits, slots orapertures can be configured to reduce or otherwise limit the amount ofeddy currents forming in the die attach paddle.

The plurality of leads can be disposed at a first height with respect tothe external conductor and the die attach paddle is disposed at asecond, different height with respect to the external conductor, whereinthe first height is greater than the second height.

In some embodiments, a mold material encloses the one or more substratesand a portion of the lead frame including the die attach paddle. A firstplurality of the leads can extend from a first side of the mold materialand a second plurality of the leads can extend from a second, oppositeside of the mold material, and the die attach paddle is attached to oneor more of the first plurality of the leads and is spaced from thesecond plurality of leads.

The plurality of magnetic field sensing elements may comprise at leastone of a Hall effect element or a magnetoresistance element. Themagnetoresistance element may comprise at least one of Indium Antimonide(InSb), a giant magnetoresistance (GMR) element, an anisotropicmagnetoresistance (AMR) element, a tunneling magnetoresistance (TMR)element or a magnetic tunnel junction (MTJ) element.

In another aspect, a current sensor system is provided comprising aprinted circuit board (PCB), a conductor supported by the PCB andconfigured to carry a current and a current sensor comprising aplurality of magnetic field sensing elements supported by one or moresubstrates. At least one of the plurality of magnetic field sensingelements is vertically aligned with the conductor and at least one ofthe plurality of magnetic field sensing elements is not verticallyaligned with the conductor.

A plurality of slots (or slits) may be formed in the conductor in adirection of the current. The slots (or slits) may be formed to reduceor otherwise mitigate adverse effects of skin effect and currentcrowding at higher current frequencies. The conductor has an edge andthe at least one first magnetic field sensing element and the at leastone second magnetic field sensing element can be positioned such thatthey are substantially equidistant from the edge.

The current sensor may further comprise a circuit responsive to a firstmagnetic field signal from the at least one magnetic field sensingelement that is vertically aligned with the conductor and to a secondmagnetic field signal from the at least one magnetic field sensingelement that is not vertically aligned with the conductor. The circuitcan be configured to generate a difference signal indicative of thedifference between the first magnetic field signal and the secondmagnetic field signal. The difference signal can be indicative of thecurrent carried by the conductor.

In some embodiments, the conductor comprises a conductive tracesupported by the PCB and proximate to the current sensor. In otherembodiments, the conductor comprises a conductive trace disposed distalfrom the current sensor such that the PCB is positioned between theconductive trace and the current sensor.

The current sensor may further comprise a lead frame having a firstsurface adjacent to the PCB and a second, opposing surface distal fromthe PCB, the lead frame comprising a die attach paddle and a pluralityof leads, and the one or more substrates attached to the die attachpaddle. In some embodiments, the one or more substrates can have a firstsurface attached to the die attach paddle and a second, opposing surfaceand the plurality of magnetic field sensing elements can be supported bythe second surface of the one or more substrates. In other embodiments,the one or more substrates can have a first surface attached to the dieattach paddle and proximate to the lead frame, and a second, opposingsurface distal from the lead frame, and the plurality of magnetic fieldsensing elements can be supported by the first surface of the one ormore substrates.

The die attach paddle may comprise one or more slits, slots orapertures. The plurality of leads can be disposed at a first height withrespect to the conductor and the die attach paddle can be disposed at asecond, different height with respect to the conductor. The first heightcan be greater than the second height.

The current sensor system may comprise a mold material enclosing the oneor more substrates and a portion of the lead frame including the dieattach paddle. A first plurality of the leads may extend from a firstside of mold material and a second plurality of the leads may extendfrom a second, opposite side of the mold material. The die attach paddlecan be attached to the first plurality of the leads and is not attachedto the second plurality of leads.

The plurality of magnetic field sensing elements may comprise at leastone of a Hall effect element or a magnetoresistance element. Themagnetoresistance element may comprise at least one of Indium Antimonide(InSb), a giant magnetoresistance (GMR) element, an anisotropicmagnetoresistance (AMR) element, a tunneling magnetoresistance (TMR)element or a magnetic tunnel junction (MTJ) element.

In another aspect, a current sensor for sensing a magnetic fieldgenerated by a current through an external conductor is providedcomprising a lead frame having a first surface and a second, opposingsurface, a die attach paddle, a first plurality of leads and a secondplurality of leads, the die attach paddle having first side adjacent tothe first plurality of leads and second, opposing side adjacent to thesecond plurality of leads, wherein the first side of the die attachpaddle is attached to at least one of the first plurality of leads andwherein the second side of the die attach paddle is spaced from thesecond plurality of leads, one or more substrates attached to the dieattach paddle and a plurality of magnetic field sensing elementssupported by the one or more substrates. At least one first magneticfield sensing element of the plurality of magnetic field sensingelements is spaced from at least one second magnetic field sensingelement of the plurality of magnetic field sensing elements such thatthe at least one first magnetic field sensing element is closer to thefirst side of the die attach paddle than to the second side of the dieattach paddle and the at least one second magnetic field sensing elementis closer to the second side of the die attach paddle than to the firstside of the die attach pad.

In some embodiments, the one or more substrates can have a first surfaceattached to the die attach paddle and a second, opposing surface and theplurality of magnetic field sensing elements can be supported by thesecond surface of the one or more substrates. In other embodiments, theone or more substrates can have a first surface attached to the dieattach paddle and proximate to the lead frame, and a second, opposingsurface distal from the lead frame and the plurality of magnetic fieldsensing elements can be supported by the first surface of the one ormore substrates.

The at least one first magnetic field sensing element can be configuredto generate a first magnetic field signal indicative of a distancebetween the at least one first magnetic field sensing element and theconductor and the at least one second magnetic field sensing element canbe configured to generate a second magnetic field signal indicative of adistance between the at least one second magnetic field sensing elementand the conductor. The current sensor may further comprise a circuitresponsive to the first magnetic field signal and to the second magneticfield signal and configured to generate a difference signal indicativeof a difference between the first magnetic field signal and the secondmagnetic field signal. The difference can be indicative of the currentcarried by the conductor.

In some embodiments, the at least one first magnetic field sensingelement is vertically aligned with the conductor and the at least onesecond magnetic field sensing element is not vertically aligned with theconductor. The die attach paddle may comprise one or more slits, slotsor apertures.

The first and second plurality of leads can be disposed at a firstheight with respect to the conductor and the die attach paddle can bedisposed at a second, different height with respect to the conductor.The first height can be greater than the second height.

The current sensor may further comprise a mold material enclosing theone or more substrates and a portion of the lead frame including the dieattach paddle. The first plurality of the leads can extend from a firstside of mold material and the second plurality of the leads can extendfrom a second, opposite side of the mold material.

The plurality of magnetic field sensing elements may comprise at leastone of a Hall effect element or a magnetoresistance element. Themagnetoresistance element may comprise at least one of Indium Antimonide(InSb), a giant magnetoresistance (GMR) element, an anisotropicmagnetoresistance (AMR) element, a tunneling magnetoresistance (TMR)element or a magnetic tunnel junction (MTJ) element.

In another aspect, a method for sensing a magnetic field generated by acurrent through an external conductor comprises providing a lead framehaving a first surface and a second, opposing surface, the lead framecomprising a die attach paddle and a plurality of leads, wherein one ormore substrates are attached to the die attach paddle, providing acurrent sensor comprising a plurality of magnetic field sensing elementssupported by a surface of one or more substrates, wherein at least onefirst magnetic field sensing element of the plurality of magnetic fieldsensing elements is spaced from at least one second magnetic fieldsensing element of the plurality of magnetic field sensing elements,sensing the magnetic field by the at least one first magnetic fieldsensing element and the at least one second magnetic field sensingelement, wherein the at least one first magnetic field sensing elementand the at least one second magnetic field sensing element areorientated to sense the magnetic field in the same direction, generatinga first magnetic field signal indicative of a first distance between theat least one first magnetic field sensing element and the conductor,generating a second magnetic field signal indicative of a seconddistance between the at least one second magnetic field sensing elementand the conductor and generating a difference signal indicative of adifference between the first magnetic field signal and the secondmagnetic field signal, wherein the difference is indicative of thecurrent carried by the conductor.

The method may further comprise positioning the at least one firstmagnetic field sensing element such that it is vertically aligned withthe conductor and positioning the at least one second magnetic fieldsensing element such that it is not vertically aligned with theconductor. One or more slits, slots or apertures may be formed in thedie attach paddle.

In some embodiments, the method further comprises disposing theplurality of leads at a first height with respect to the conductor anddisposing the die attach paddle at a second, different height withrespect to the conductor. The first height can be greater than thesecond height.

The one or more substrates and a portion of the lead frame including thedie attach paddle may be enclosed in a mold material. A first pluralityof the leads may extend from a first side of mold material and a secondplurality of the leads may extend from a second, opposite side of themold material. The die attach paddle can be attached to one or more ofthe first plurality of the leads and is spaced from the second pluralityof leads.

The plurality of magnetic field sensing elements may comprise at leastone of a Hall effect element or a magnetoresistance element. Themagnetoresistance element may comprise at least one of Indium Antimonide(InSb), a giant magnetoresistance (GMR) element, an anisotropicmagnetoresistance (AMR) element, a tunneling magnetoresistance (TMR)element or a magnetic tunnel junction (MTJ) element.

In another aspect, a method for sensing a magnetic field generated by acurrent through a conductor is provided comprising providing a printedcircuit board (PCB) supporting the conductor, providing a current sensorcomprising a plurality of magnetic field sensing elements supported byone or more substrates, positioning the current sensor over an edge ofthe conductor such that a first magnetic field sensing element of theplurality of magnetic field sensing elements is vertically aligned withthe conductor and a second magnetic field sensing element of theplurality of magnetic field sensing elements is it not verticallyaligned with the conductor; wherein the conductor is supported by thePCB and configured to carry the current, and computing a differencebetween a first magnetic field signal generated by the first magneticfield sensing element and a second magnetic field signal generated bythe second magnetic field sensing element, wherein the difference isindicative of the current through the conductor.

The method may further comprise forming a plurality of slots formed inthe conductor in a direction of the current. In some embodiments,positioning the current sensor over the edge of the conductor comprisespositioning the at least one first magnetic field sensing element andthe at least one second magnetic field sensing element such that theyare substantially equidistant from the edge.

The method may further comprise providing the conductor as a conductivetrace disposed distal from the current sensor such that the PCB ispositioned between the conductive trace and the current sensor.

In some embodiments, providing the current sensor further comprisesproviding a lead frame having a first surface adjacent to the PCB and asecond, opposing surface distal from the PCB, the lead frame comprisinga die attach paddle and a plurality of leads. A first surface of the oneor more substrates can be coupled to the die attach paddle, wherein theplurality of magnetic field sensing elements can be supported by asecond, opposite surface of the one or more substrates. In otherembodiments, a first surface of the one or more substrates can becoupled to the die attach paddle, wherein the plurality of magneticfield sensing elements can be supported by the first surface of the oneor more substrates.

One or more slits, slots or apertures in the die attach paddle. Themethod may further comprise providing the plurality of leads at a firstheight with respect to the conductor and providing the die attach paddleat a second, different height with respect to the conductor. The firstheight can be greater than the second height.

The method may further comprise enclosing the one or more substrates anda portion of the lead frame including the die attach paddle in a moldmaterial. A first plurality of the leads may extend from a first side ofmold material and a second plurality of the leads may extend from asecond, opposite side of the mold material. The die attach paddle can beattached to one or more of the first plurality of the leads and is notattached to the second plurality of leads.

The plurality of magnetic field sensing elements may comprise at leastone of a Hall effect element or a magnetoresistance element. Themagnetoresistance element may comprise at least one of Indium Antimonide(InSb), a giant magnetoresistance (GMR) element, an anisotropicmagnetoresistance (AMR) element, a tunneling magnetoresistance (TMR)element or a magnetic tunnel junction (MTJ) element.

In another aspect, a current sensor for sensing a magnetic fieldgenerated by a current through an external conductor, the magnetic fieldhaving direction associated with a direction of the current through theconductor, comprises a first means for sensing the magnetic fieldgenerated by the current to generate a first magnetic field signalindicative of a distance between the first magnetic field sensing meansand the conductor, a second means for sensing the magnetic fieldgenerated by the current to generate a second magnetic field signalindicative of a distance between the second magnetic field sensing meansand the conductor, means for supporting the first magnetic field sensingmeans and the second magnetic field sensing means in a spacedrelationship, but with both the first and second magnetic field sensingmeans oriented to sense the magnetic field in the same direction andmeans for determining a difference between the first magnetic fieldsignal and the second magnetic field signal, wherein the difference isindicative of the current through the conductor.

The first magnetic field sensing means can be vertically aligned withthe external conductor and the second magnetic field sensing means canbe positioned such that it is not vertically aligned with the externalconductor.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features may be more fully understood from the followingdescription of the drawings in which:

FIG. 1 shows a current sensor having a plurality of magnetic fieldsensing elements supported by a substrate and attached to a die attachpaddle;

FIG. 1A shows an exploded view of the current sensor of FIG. 1;

FIG. 2 shows the current sensor of FIG. 1 positioned over an edge of aconductor;

FIG. 2A shows the spacing of one or more magnetic field sensing elementswithin the current sensor of FIG. 1 relative to the conductor;

FIG. 2B shows one or more slits formed in a conductor;

FIGS. 2C-2F show different embodiments of conductors comprising one ormore conductive traces and a printed circuit board relative to thecurrent sensor of FIG. 1;

FIG. 3 is a plain view of the current sensor of FIG. 1;

FIG. 4 is a circuit diagram of a current sensor;

FIG. 5 is a flow diagram of a method for sensing a magnetic fieldgenerated by a current through a conductor by the current sensor of FIG.1;

FIG. 6 is a flow diagram of a method for sensing a magnetic fieldgenerated by a current though a conductor by the current sensor of FIG.1.

FIG. 7 shows a flip chip current sensor; and

FIG. 7A shows a side view of the flip chip current sensor of FIG. 7.

DETAILED DESCRIPTION

Before describing the present invention, some introductory concepts andterminology are explained.

As used herein, the term “magnetic field sensing element” is used todescribe a variety of electronic elements that can sense a magneticfield. The magnetic field sensing element can be, but is not limited to,a Hall-effect element, a magnetoresistance element, or amagnetotransistor. As is known, there are different types of Hall-effectelements, for example, a planar Hall element, a vertical Hall element,and a Circular Vertical Hall (CVH) element. As is also known, there aredifferent types of magnetoresistance elements, for example, asemiconductor magnetoresistance element such as an Indium Antimonide(InSb) element, a giant magnetoresistance (GMR) element, for example, aspin valve, an anisotropic magnetoresistance element (AMR), a tunnelingmagnetoresistance (TMR) element, and a magnetic tunnel junction (MTJ).The magnetic field sensing element may be a single element or,alternatively, may include two or more magnetic field sensing elementsarranged in various configurations, e.g., a half bridge or full(Wheatstone) bridge. Depending on the device type and other applicationrequirements, the magnetic field sensing element may be a device made ofa type IV semiconductor material such as Silicon (Si) or Germanium (Ge),or a type III-V semiconductor material like Gallium-Arsenide (GaAs) oran Indium compound, e.g., Indium-Antimonide (InSb).

As is known, some of the above-described magnetic field sensing elementstend to have an axis of maximum sensitivity parallel to a substrate thatsupports the magnetic field sensing element, and others of theabove-described magnetic field sensing elements tend to have an axis ofmaximum sensitivity perpendicular to a substrate that supports themagnetic field sensing element. In particular, planar Hall elements tendto have axes of sensitivity perpendicular to a substrate, while metalbased or metallic magnetoresistance elements (e.g., GMR, TMR, AMR) andvertical Hall elements tend to have axes of sensitivity parallel to asubstrate.

As used herein, the term “magnetic field sensing circuit” is used todescribe a circuit that uses a magnetic field sensing element, generallyin combination with other circuits. Magnetic field sensing circuits areused in a variety of applications, including, but not limited to, anangle sensor that senses an angle of a direction of a magnetic field, acurrent sensor that senses a magnetic field generated by a currentcarried by a current-carrying conductor, a magnetic switch that sensesthe proximity of a ferromagnetic object, a rotation detector that sensespassing ferromagnetic articles, for example, magnetic domains of a ringmagnet or a ferromagnetic target (e.g., gear teeth) where the magneticfield sensor is used in combination with a back-biased or other magnet,and a magnetic field sensor that senses a magnetic field density of amagnetic field.

Now referring to FIG. 1, a current sensor 100 includes a lead frame 102,a substrate 108 and a plurality of magnetic field sensing elements 110a-110 n supported by substrate 108. Current sensor 100 can be positionedover an edge of an external conductor (FIG. 2) and be configured toperform current sensing based at least in part on a relative spacingbetween each of the at least two of the magnetic field sensing elements110 a-110 n and the conductor.

Magnetic field sensing elements 110 a-110 n are oriented or otherwisepositioned such that each of the magnetic field sensing elements 110a-110 n can sense a magnetic field generated by a current through anexternal conductor (FIG. 2) in the same direction. However, each of themagnetic field sensing elements 110 a-110 n can be positioned atdifferent distances from the external conductor and thus generatemagnetic field signals at different levels based at least in part ontheir respective distance from the external conductor. A differencebetween the magnetic field signals generated by each of the magneticfield sensing elements 110 a-110 n can be used to determine the currentthrough the external conductor. Further, the spacing between at leastone first magnetic sensing element 110 a and at least one secondmagnetic field sensing element 110 n may be selected to optimize thegradient between the magnetic fields experienced by each of the sensingelements 110 a, 110 n.

Lead frame 102 includes a die attach paddle 104 and a plurality of leads106. Substrate (e.g., semiconductor substrate) or die 108 is attached todie attach paddle 104, as may be achieved with an adhesive layer 107.For example, and as illustrated in FIG. 1, a second surface 108 b ofsubstrate 108 is coupled to a first surface 104 a of die attach paddle104 (i.e., die-up configuration). It should be appreciated however, thatin other embodiments, a first surface 108 a of substrate 108 may becoupled to a second surface 104 b of die attach paddle 104 (i.e., flipchip configuration as shown in FIG. 7). It will also be understood thatwhile a single semiconductor die 108 is shown, the current sensor caninclude more than one die, with each such die supporting magnetic fieldsensing element(s) and/or supporting circuitry.

Lead frame 102 can be configured to provide high voltage isolationbetween signal leads as may carry relatively low voltage signals andhigh voltage leads as may contact an external conductor. For example,leads 106 includes a first plurality of leads 106 a extending from afirst side 104 c of die attach paddle 104 and a second plurality ofleads 106 b spaced from (e.g., not in contact with) a second side 104 dof die attach paddle 104. Leads 106 a may be coupled to a non-currentcarrying surface and leads 106 b may be coupled to a current carryingsurface of a conductor. For example, in some embodiments, leads 106 amay be coupled to a microcontroller or other surface that may utilizelow voltage current measurement signals. It should be appreciated that anon-current carrying surface as referred to herein may refer to a lowvoltage surface or a surface carry a current less than a currentcarrying surface of a conductor (e.g., conductor 206 of FIG. 2.). Thus,leads 106 b (coupled to current carrying conductor) may be electricallyisolated from die attach paddle 104. The space gap between leads 106 band die attach paddle 104 is shown further below in connection with FIG.3.

It should be appreciated that in the current sensor arrangementsdescribed herein, the conductor (e.g., conductor 206 of FIG. 2.) can beisolated from the one or more substrates 108 and first plurality ofleads 106 a through a variety of different techniques. For example, insome embodiments, to provide voltage isolation, die attach paddle 104can be coupled to second plurality of leads 106 b. However, an isolationlayer (e.g., tape, non-conductive die attach paddle) can be disposedbetween the one or more substrates 108 and die attach paddle 104 and oneor more wire bonds can be coupled from the one or more substrates 108 tothe signal leads.

Die attach paddle 104 may include one or more cutouts, slits, slots orapertures 114 a, 114 b to reduce eddy currents. For example, eddycurrents may be formed near a current carrying conductor and opposemagnetic fields, generated by the current carrying conductor that are tobe sensed by magnetic field sensing elements 110 a-110 n. The one ormore cutouts 114 a, 114 b may be configured to limit the amount of eddycurrents forming in the die attach paddle 104. The one or more cutouts114 a, 114 b will be described in greater detail below with respect toFIG. 3.

Substrate 108 may include a semiconductor substrate. In someembodiments, substrate 108 may include a semiconductor material and anymaterial used for supporting semiconductor materials. For example,substrate 108 may include, but not limited to, a semiconductor materialdisposed on at least one of glass, ceramic, or polymer.

A mold material 116 is provided to enclose die attach paddle 104,substrate 108, magnetic field sensing elements 110 a-110 n and portionsof leads 106, as shown.

Magnetic field sensing elements 110 a-110 n may include one or more Halleffect elements or one or more magnetoresistance elements. For example,the magnetoresistance elements may include at least one of IndiumAntimonide (InSb), a giant magnetoresistance (GMR) element, ananisotropic magnetoresistance (AMR) element, a tunnelingmagnetoresistance (TMR) element or a magnetic tunnel junction (MTJ)element.

In an embodiment, current sensor lead frame can have a downsetconfiguration such that portions of the plurality of leads 106 arepositioned at different heights than the die attach paddle 104 (andthus, also than the substrate 108 and magnetic field sensing elements110 a-110 n).

For example, and referring also to the exploded view of current sensor150 in FIG. 1A, leads 106 a include a first portion 140 a at a firstheight and a connect portion 142 coupled between the first portion 140 aand the die attach paddle 104. Thus, the first lead portions 140 a canbe at a first height and the die attach paddle 104 can be at a differentheight that in some embodiments is less than the first height. In suchembodiments, when the current sensor is positioned relative to a currentcarrying conductor, the first lead portions 140 a may be higher than thedie attach paddle 104 relative to the conductor, in order to therebybring the die attach paddle closer to the conductor than otherwisepossible.

A second portion 140 b of leads 106 a may be at a second lower heightthan portions 140 a to provide surface mount pads for coupling to aprinted circuit board or other support structure. Similarly leads 106 bcan have a first portion 144 a at a first height and second portions 144b at a second, lower height to form surface mount pads.

The first portion 144 a of leads 106 b can be spaced from (i.e., not incontact with) die attach paddle 104. Thus, in applications in whichleads 106 b are coupled to a current carrying conductor (see, e.g., FIG.2), die attach paddle 104 and electrically coupled leads 106 a can beelectrically isolated from the current carrying conductor.

Now referring to FIG. 2, a current sensor 200 is positioned over an edge212 of external conductor 206 that is configured to carry a current 210.Current sensor 200 may be the same as or substantially similar tocurrent sensor 100 of FIG. 1 and thus may include a plurality ofmagnetic field sensing elements configured to sense a magnetic fieldgenerated by the current 210 through conductor 206. In an embodiment,the plurality of magnetic field sensing elements can be oriented orotherwise positioned within current sensor 200 to sense the magneticfield generated by current 210 through conductor 206 in the samedirection. In other words, the magnetic field sensing elements arepositioned within the sensor package 200 such that when the sensor 200is disposed in proximity to (i.e., disposed over) the conductor 206, themagnetic field (generated by the current through the conductor) incidenton each of the sensing elements has the same polarity.

As illustrated in FIG. 2, a first plurality of leads 204 a of currentsensor 200 are coupled to a non-current carrying surface 208 and asecond plurality of leads 204 b are coupled to conductor 206. Thus,current sensor 200 can be positioned over edge 212 of conductor 206, asshown. First plurality of leads 204 a and second plurality of leads 204b may be the same as or substantially similar to respective leads 106 aand leads 106 b of current sensor 100 of FIG. 1. Thus, in an embodiment,leads 204 a may be coupled to a die attach paddle within current sensor200 and leads 204 b may be spaced from (e.g., not in contact with) thedie attach paddle within current sensor 200. Thus, current sensor 200may provide high voltage isolation between leads 204 a and conductor206.

Referring also to FIG. 2A, current sensor 200 can be positioned overedge 212 of conductor 206 such that a first magnetic sensing element 260is vertically aligned with (here over) conductor 206 and a secondmagnetic sensing element 262 is not vertically aligned with conductor206 and instead is aligned with a non-current carrying surface 208(i.e., with magnetic field sensing elements 260, 262 straddling the edge212 of the conductor). Current sensor 200 can be configured to performcurrent sensing by comparing (e.g., subtracting) outputs of first andsecond magnetic field sensing elements 260, 262 in order to therebysense the current by sensing a gradient between the magnetic fieldsensed by each sensing element 260, 262. Thus, the sensing methodologyrequires a difference (or gradient) in the magnetic fields experiencedby the sensing elements 260, 262.

The position of current sensor 200 relative to conductor 206 can beselected based at least in part on a level of the current throughconductor 206 and thus, the expected magnetic field strength, thesensitivity of the magnetic field sensing elements, and/or a magneticfield gradient to be measured. In some embodiments, it may be desirableto position the sensor 200 so that the sensing elements 260, 262experience the largest magnetic field gradient possible (i.e., thelargest difference between the magnetic fields experienced by the spacedmagnetic field sensing elements 260, 262) as may occur when at least onefirst magnetic sensing element 260 is vertically aligned with thecurrent carrying conductor 206 and at least one second magnetic sensingelement 262 is not vertically aligned with the current carryingconductor 206. To this end, a first portion 200 a of current sensor 200is vertically aligned with (here over) conductor 206 and a secondportion 200 b is not vertically aligned with conductor 206 and insteadis vertically aligned with a non-current carrying surface 208. In onesuch configuration, current sensor 200 may be positioned such that anedge 200 c of first portion 200 a and an edge 200 d of second portion200 b are equidistant from edge 212 of conductor 206, here representedby a distance “d1” (and more specifically such that the sensing elements260, 262 are equidistant from the conductor edge 212, here representedby a distance “d2”). Thus, first portion 200 a and second portion 200 bcan be equal in size (e.g., width, length).

In other embodiments, first portion 200 a and second portion 200 b maybe different in size. For example, current sensor 200 may be positionedsuch a distance from edge 212 of conductor 206 to edge 200 c of firstportion 200 a is greater than a distance from edge 212 of conductor 206to edge 200 d of second portion 200 b. In other embodiments, currentsensor 200 may be positioned such a distance from edge 212 of conductor206 to edge 200 c of first portion 200 a is less than a distance fromedge 212 of conductor 206 to edge 200 d of second portion 200 b. In suchconfigurations, the magnetic field sensing elements 260, 262 may not beequidistantly spaced from the conductor edge 212.

In some embodiments, all of current sensor 200 (or at least bothmagnetic field sensing elements 260, 262) may be vertically aligned(i.e., positioned over) conductor 206. In such embodiments, the sensingelements 260, 262 are not centered with respect to the conductor inorder to ensure a gradient in the magnetic fields experienced by thesensing elements. In other embodiments, current sensor 200 can bepositioned relative to conductor 206 such no portion (or at leastneither magnetic field sensing element) is vertically aligned (i.e.,positioned over) conductor 206 and instead current sensor 200 isvertically offset with respect to conductor 206.

It should be appreciated that although current sensor 200 is shown toinclude two magnetic field sensing elements 260, 262 in FIG. 2A, inother embodiments, current sensor 200 (or any current sensor describedherein) may include more than two magnetic field sensing elements.

Now referring to FIG. 2B, conductor 282 is provided having one or moreslits 284 a-284 n (here four). Conductor 282 may be the same as orsubstantially similar to conductor 206 of FIGS. 2-2A, however, conductor282 includes slits 284 a-284 n. Slits 284 a-284 n may be formed toreduce or otherwise mitigate adverse effects of skin effect and currentcrowding at higher current frequencies. For example, as current flowsthrough conductor 282 at high frequency, the current tends to crowd ormigrate towards the outer surfaces and edges of conductor 282. Conductorslits 284 a-284 n have the effect of making the conductor 282 presentelectrical characteristics as if the current were being carried bymultiple parallel wires, the number of wires being based on the numberof slits 284 a-284 n in order to thereby normalize or otherwise equalizethe current sensor response over frequency.

The slits 284 a-284 n may be formed such that their length issubstantially parallel to a direction of the current flow through theconductor. In some embodiments, multiple slits 284 a-284 n may be formedsuch that they are equidistant from each other. In other embodiments,multiple slits 284 a-284 n may be formed such that they have differentdistances between them. The total number of slits 284 a-284 n may varybased at least in part on properties of conductor 282 and/or aparticular application of a current sensor. For example, in someembodiments, conductor 282 may have one slit 284 a-284 n. In otherembodiments, conductor 282 may have two or more slits 284 a-284 n.

Now referring to FIGS. 2C-2F, conductor 206 may take the form of aconductive trace 220 and a printed circuit board (PCB) 224. It should beappreciated that in some embodiments, each of the current tracesillustrated in FIGS. 2C-2F may include one or more slits, such as slits284 a-284 n described above with respect to FIG. 2B. Conductive trace220 may be formed, disposed on or otherwise supported by one or moresurfaces of the PCB 224. For example, and as illustrated in FIG. 2C (inwhich the current can be considered to flow into the page), conductivetrace 220 may be supported by a first surface 224 a of PCB 224 such thatconductive trace is disposed proximal to current sensor 200.

In FIG. 2D, a first conductive trace 220 a is supported by first surface224 a of PCB 224 and a second conductive trace 220 b is supported by asecond opposite surface 224 b of PCB 224. Current can be considered toflow into the page through both the first and second conductive traces220 a, 220 b. This configuration can allow for higher current flow thanotherwise possible, while also maintaining thermal performance.

In FIG. 2E, first conductive trace 220 a is supported by first surface224 a of PCB 224 and second conductive trace 220 b is supported bysecond opposite surface 224 b of PCB 224 and one or more additionalconductive trace layers 220 c are embedded within PCB 224. Current canbe considered to flow into the page through both the conductive traces220 a, 220 b, and 220 c. This configuration can allow for maximumcurrent flow, while also maintaining thermal performance. In embodimentsin which the conductor is comprised of more than one conductive trace(e.g., FIGS. 2D and 2E), it will be appreciated that the multipleconductive traces can be electrically coupled in parallel so thatcurrent to be sensed by current sensor 200 flows in parallel through themultiple conductive traces. In some embodiments, the multiple conductivetraces can be electrically coupled in series so that current to besensed by current sensor 200 flows in series through the multipleconductive traces to increase the current to be sensed by current sensor200 and improve sensor resolution.

In other embodiments and as illustrated in FIG. 2F, conductive trace 220may be supported by second surface 224 b of PCB 224 such that conductivetrace 220 is disposed distal from current sensor 200 and PCB 224 isdisposed between conductive trace 220 and current sensor 200. Hereagain, current can be considered to flow into the page. Thisconfiguration provides a very high level of voltage isolation. It shouldbe appreciated, that in the embodiment of FIG. 2F, current sensor 200 iscoupled to a first surface 224 a of PCB 224 and conductive trace 220 issupported by the second surface 224 b to provide the voltage isolation.Thus, in some embodiments, secondary leads extending from current sensor200 can be coupled to current sensor 200 and not isolated or otherwisespaced apart from current sensor 200 (in contrast to current sensor 100described above with respect to FIG. 1).

Now referring to FIG. 3, a current sensor 300 is provided having a leadframe 302, the lead frame comprising a die attach paddle 304, a firstplurality of leads 306 a and a second plurality of leads 306 b. Asubstrate 308 is coupled to die attach paddle 304. A first surface 308 aof substrate 308 supports a first magnetic field sensing element 310 aand a second magnetic field sensing element 310 b.

Die attach paddle 304 may include one or more cutouts 314 a, 314 b (orslits, slots, apertures or other features) to limit or otherwise reducethe amount of eddy currents forming in die attach paddle 304 which mayaffect magnetic field sensing elements 310 a, 310 b. For example, eddycurrents may be formed near a current carrying conductor and opposemagnetic fields generated by the current carrying conductor that are tobe sensed by magnetic field sensing elements 310 a, 310 b. Thus, one ormore cutouts 314 a, 314 b (here two) may be formed in die attach paddle304 to reduce eddy currents.

As illustrated in FIG. 3, a first cutout 314 a and a second cutout 314 bmay be formed such that each is aligned with (here under) at least oneof magnetic field sensing elements 310 a, 310 b respectively. In otherembodiments, cutouts 314 a, 314 b may be formed such that one or bothare not generally aligned (e.g., not centered) with respect to at leastone of magnetic field sensing elements 310 a, 310 b.

Second plurality of leads 306 b are spaced a distance “x” from dieattach paddle 304 and thus not in contact with die attach paddle. Thespacing “x” may be selected to isolate die attach paddle 304 from acurrent carrying conductor to which the second plurality of leads 306 bmay be coupled. In some embodiments, the spacing “x” may be selectedbased at least in part on a level of the current through or voltage atthe conductor and/or isolation requirements.

Now referring to FIG. 4, a current sensor system 400 includes a currentsensor 404 and conductor 402. Current sensor 404 may be the same as, orsubstantially similar to current sensor 100 of FIG. 1. Current sensor404 includes at least two spaced magnetic field sensing elements 405 anda controller circuit 436. Controller circuit 436 can generate variouscontrol signals to control processing the output signals of magneticfield sensing elements 405 in order to thereby provide a current sensoroutput signal 428 indicative of a level of current through conductor402. It should be appreciated that the output signals of the magneticfield sensing elements can be proportional to the current carried byconductor 402 and that the proportionality constant can be indicative ofthe distance between the respective magnetic field sensing elements ofcurrent sensor 404.

An input/output circuit (I/O) 438 coupled to controller 436 can controlcommunication between current sensor 404 and various external devices orsystems, such as an Engine Control Unit (ECU) in automotive applicationsof the current sensor system 400. For example, in some embodiments, I/Ocircuit 438 may include a clock (SCL) pin to receive a clock signal anda data (SDA) pin to receive and/or send a data signal. The currentsensor system 400 may include a power module 440 to power circuitrywithin the sensor. For example, the power module 440 may include aregulator configured to receive power from a battery.

Current sensor 404 is positioned proximate to conductor 402 to sense amagnetic field generated by a current through conductor 402. To thisend, current sensor 404 includes magnetic field sensing elements 405responsive to receive a driver signal 407 from a bridge driver 406. Inthe example, current sensor 404 of FIG. 4, magnetic field sensingelements 405 include four magnetoresistance elements coupled in a bridgeconfiguration, such as a Wheatstone bridge. For example,magnetoresistance elements 405 may be coupled such that each leg of thebridge includes two magnetoresistance elements positioned adjacent toone another, with one such leg spaced from the other leg. For example,magnetoresistance elements 405 may be coupled such that each leg of thebridge includes two magnetoresistance elements positioned diagonal fromeach other to form each respective leg of the bridge or group ofelements (e.g., element in left leg upper position and element in rightleg lower position form a first bridge leg and element in left leg lowerposition and element in right leg upper position form a second bridge).

With this arrangement, a differential output signal of the bridge (takenbetween intermediate nodes of each bridge leg) may result in adifferential signal that rejects stray fields from sources other thanthe current through the conductor 402. For example, one bridge leg canprovide sensing element 260 (FIG. 2A) and the other bridge leg canprovide sensing element 262 (FIG. 2A) so that the resulting differentialsignal is indicative of the difference between the magnetic field sensedby each bridge leg. The magnetoresistance elements 405 may include atleast one of at least one of an Indium Antimonide (InSb) element, agiant magnetoresistance (GMR) element, an anisotropic magnetoresistance(AMR) element, a tunneling magnetoresistance (TMR) element or a magnetictunnel junction (MTJ) element. It should be appreciated that, in someembodiments, magnetic field sensing elements 405 may be provided as oneor more Hall effect elements.

Controller circuit 436 can include or be coupled to a bridge trimcircuit 408 configured to improve the accuracy of the current sensoroutput signal 428 by trimming the sensing elements of the bridge 405.For example, in the presence of a reference magnetic field (as may beapplied during production), bridge trim circuit 408 can provide a trimsignal 409 to magnetic field sensing elements 405 to trim the elementsof the bridge 504 in order to thereby ensure that the sensitivity of theindividual elements and/or legs of the bridge is matched.

Magnetic field sensing elements 405 can generate a differential magneticfield signal for coupling to a first differential amplifier 410. One ormore outputs of first amplifier 410 are coupled to one or more inputs ofan H bridge circuit 412. H bridge circuit 412 can include multiple fieldeffect transistors coupled together to compare two input signals andremove or reduce noise and/or interference (e.g., DC offset) and in someembodiments, apply a gain to the difference between the two inputsignals.

A compensation coil 414 can be positioned proximate to magnetic fieldsensing elements 405 in order to apply an equal and opposite field tothe sensing elements 405 drive the differential field on the bridge tozero Gauss. The current through coil 414 necessary to bring thedifferential field on the sensing elements 405 to zero is sensed by aresistor 416 in order to thereby implement a closed loop current sensingsystem. It should be appreciated that although current sensor 404 isshown to be a closed loop sensor in FIG. 4, in some embodiments, currentsensor 404 can be an open loop sensor.

A voltage on the sense resistor 416 is coupled to further amplifiers 418and 420 to implement offset and gain adjustment, including temperaturecompensation. An output terminal 428 of current sensor 404 (e.g., VOUT)can be provided at the output of amplifier 420 to provide a signalhaving a level indicative of the current through the conductor 402.

A differential comparator 422 can be provided to implement a faultdetection feature. To this end, a logic gate 424 has a first inputcoupled to the output of comparator 422 and a second input coupled to aninterrupt signal 425. In some embodiments, logic gate 424 may include anOR gate. An output of logic gate 424 is coupled to a control input of atransistor 426 such that detection of a current greater than apredetermined level causes a fault signal 430 to be provided. Currentsensor 404 can include an analog-to-digital converter (ADC) 434 can beconfigured to monitor analog signals within current sensor 404 (e.g.,analog references).

Now referring to FIG. 5, a method 500 for sensing a magnetic fieldgenerated by a current through an external conductor begins at block502, by providing a current sensor comprising a plurality of magneticfield sensing elements supported by a first surface of a substrate. Atleast one first magnetic field sensing element (hereinafter firstmagnetic field sensing element) can be spaced from at least one secondmagnetic field sensing element (hereinafter second magnetic fieldsensing element). It should be appreciated that the followingdescription describes a current sensor having two magnetic field sensingelements, however a current sensor as described herein may include morethan two magnetic field sensing elements.

The current sensor can include a lead frame having a die attach paddleand a plurality of leads. The substrate can be coupled to the die attachpaddle. The plurality of leads can include a first plurality of leadscoupled to the die attach paddle and a second plurality of leads spacedfrom the die attach paddle. For example, the first plurality of leadscan be coupled to and extend from a first side of the die attach paddleand the second plurality of leads can be spaced from a second side ofthe die attach paddle.

The current sensor can be positioned proximate to a current carryingexternal conductor (e.g., external to the current sensor) to sense amagnetic field generated by the current through the conductor. The firstplurality of leads may be coupled to a non-current carrying surface andthe second plurality of leads may be coupled to the current carryingconductor. The second plurality of leads are spaced from the die attachpaddle, thus, the die attach paddle may be isolated from the currentcarrying conductor.

One or more cutouts may be formed in the die attach paddle. The one ormore cutouts can be formed such that they are aligned with at least onemagnetic field sensing element. For example, in one embodiment, the oneor more slots may be formed such that each of them are under at leastone magnetic field sensing element.

In some embodiments, one or more slits may be formed in the conductor.Slits in the conductor may be aligned substantially with a direction ofthe current flow. For example, in some embodiments, the slits can beformed such that they are generally parallel with a direction of thecurrent. In some embodiments having multiple slits, the slits may beformed such that they are spaced equidistant from each other. In otherembodiments having multiple slits, the slits may be formed such thatthey are spaced at varying distances from a first slit to a nextadjacent slit.

The current sensor may be formed having a downset configuration. Forexample, the plurality of leads can be positioned at a first height withrespect to the conductor and the die attach paddle can be positioned ata second height with respect to the conductor. The first height can begreater than the second height such that the die attach paddle,substrate and plurality of magnetic field sensing elements are disposedat a lower height and in a closer proximity to the current carryingconductor than otherwise possible.

In some embodiments, a mold material may enclose the die attach paddle,a portion of the plurality of leads, and the substrate to form a currentsensor package. The first plurality of the leads can extend from a firstside of mold material and the second plurality of the leads can extendfrom a second, opposite side of the mold material.

At block 504, the current though the external conductor can be sensed bythe first magnetic field sensing element and the second magnetic fieldsensing element. The current sensor can be positioned such that thefirst magnetic field sensing element is vertically aligned with thecurrent carrying conductor and the second magnetic field sensing elementis not vertically aligned with the conductor and instead is positionedover a non-current carrying surface. However, both the first magneticfield sensing element and the second magnetic field sensing element canbe oriented such that they sense the current in the same direction.

At block 506, a first magnetic field signal indicative of a firstdistance between the first magnetic field sensing element and theconductor is generated. The first magnetic field sensing element can beconfigured to generate the first magnetic field signal based at least inpart on a distance between the first magnetic field sensing element andthe conductor.

At block 508, a second magnetic field signal indicative of a seconddistance between the second magnetic field sensing element and theconductor. The second magnetic field sensing element can be configuredto generate the second magnetic field signal based at least in part on adistance between the second magnetic field sensing element and theconductor. In an embodiment, the first and second magnetic field signalscan be proportional to the current carried by the conductor and that theproportionality constant can be indicative of the distance between therespective magnetic field sensing elements.

The first and second magnetic field sensing elements are positioned atdifferent distances from the conductor and thus the first magnetic fieldsignal and the second magnetic field signal can be generated atdifferent levels based on a difference in their respective distance fromthe conductor. For example, and as discussed above, the first magneticfield sensing element can be positioned over the conductor and thesecond magnetic field sensing element can be positioned such that it isnot over the conductor, thus the first magnetic field signal may be at afirst level and the second magnetic field signal may be at a second,different level.

At block 510, a difference signal can be generated indicative of adifference between the first magnetic field signal and the secondmagnetic field signal. In an embodiment, the difference signal can beindicative of the current carried by the conductor.

Now referring to FIG. 6, a method 600 for sensing a magnetic fieldgenerated by a current through a conductor begins at block 602 byproviding a current sensor comprising a plurality of magnetic fieldsensing elements. A first magnetic field sensing element can be spacedfrom a second magnetic field sensing element within the current sensor.

The current sensor includes a lead frame having a die attach paddle anda plurality of leads. The substrate can be coupled to the die attachpaddle. The plurality of leads can include a first plurality of leadscoupled to the die attach paddle and a second plurality of leads spacedfrom the die attach paddle. For example, the first plurality of leadscan be coupled to and extend from a first side of the die attach paddleand the second plurality of leads can be spaced from a second side ofthe die attach paddle.

At block 604, the current sensor can be positioned over an edge of theconductor such that at least one first magnetic field sensing element isvertically aligned with the conductor and at least one second magneticfield sensing element is not vertically aligned with the conductor. Withthis configuration, the first and second magnetic field elements willexperience a different magnetic field strength as a result of the fieldgenerated by the current through the conductor and the differencebetween these sensed magnetic fields can be used to detect the currentlevel.

At block 606, a difference between a first magnetic field signalgenerated by the at least one first magnetic field sensing element and asecond magnetic field signal generated by the at least one secondmagnetic field sensing element can be computed. The difference can beindicative of the current carried by the conductor.

Now referring to FIGS. 7-7A, a current sensor 700 includes a lead frame702, a substrate 708 and a plurality of magnetic field sensing elements710 a-710 n supported by substrate 708. Lead frame 702 includes a firstplurality of leads 706 a and a second plurality of leads 706 b.Substrate 708 includes a first surface 708 a positioned proximate toleads 706 a, 706 b and a second surface 708 b positioned distal fromleads 706 a, 706 b. In the illustrative embodiment of FIG. 7, currentsensor 700 is provided having a flip chip arrangement. For example,plurality of magnetic field sensing elements 710 a-710 n are supportedby the first surface 708 a of substrate 708 and thus proximate to leads706 a, 706 b.

In an embodiment, current sensor 700 can be positioned over an edge ofan external conductor (FIG. 2) and be configured to perform currentsensing based at least in part on a relative spacing between each of theat least two of the magnetic field sensing elements 710 a-710 n and theconductor. Lead frame 702 can be configured to provide high voltageisolation between signal leads as may carry relatively low voltagesignals and high voltage leads as may contact an external conductor. Forexample, first plurality of leads 706 a can extend from a first side 708c of substrate 708 and second plurality of leads 706 b can be spacedfrom (e.g., not in contact with) a second side 708 d of substrate 708.Leads 706 a may be coupled to a non-current carrying surface and leads706 b may be coupled to a current carrying surface of a conductor.

For example, in some embodiments, leads 706 a may be coupled to amicrocontroller or other surface that may utilize low voltage currentmeasurement signals. It should be appreciated that a non-currentcarrying surface as referred to herein may refer to a low voltagesurface or a surface carry a current less than a current carryingsurface of a conductor (e.g., conductor 206 of FIG. 2.). Thus, leads 706b (coupled to current carrying conductor) may be electrically isolatedfrom substrate 708.

As illustrated in FIG. 7A, a plurality of solder bumps 720 a, 720 b maybe disposed between substrate 708 and first plurality of leads 706 a.Second plurality of leads 706 b are spaced from second side 708 d ofsubstrate 708. In an embodiment, one or more solder bumps 720 a-720 nmay be disposed on one or more of first plurality of leads 706 a tocouple substrate 708 to first plurality of leads 706 a. It should beappreciated that, in some embodiments, current sensor 700 having a flipchip configuration may include a die attach (not shown).

A mold material 716 may enclose the substrate 708 and a portion of firstand second plurality of leads 706 a, 706 b to form a current sensorpackage. First plurality of the leads 706 a can extend from a first sideof mold material 716 and second plurality of the leads 706 b can extendfrom a second, opposite side of the mold material 716.

Having described preferred embodiments, which serve to illustratevarious concepts, structures and techniques, which are the subject ofthis patent, it will now become apparent that other embodimentsincorporating these concepts, structures and techniques may be used.Accordingly, it is submitted that the scope of the patent should not belimited to the described embodiments but rather should be limited onlyby the spirit and scope of the following claims.

What is claimed:
 1. A current sensor for sensing a magnetic fieldgenerated by a current through an external conductor comprising: a leadframe having a first surface and a second, opposing surface, the leadframe comprising a plurality of leads; one or more substrates attachedto the lead frame; a plurality of magnetic field sensing elementssupported by the one or more substrates, wherein at least one firstmagnetic field sensing element of the plurality of magnetic fieldsensing elements is spaced from at least one second magnetic fieldsensing element of the plurality of magnetic field sensing elements,wherein the at least one first magnetic field sensing element and the atleast one second magnetic field sensing element are orientated to sensethe magnetic field in the same direction, wherein the at least one firstmagnetic field sensing element is configured to generate a firstmagnetic field signal indicative of a first distance between the atleast one first magnetic field sensing element and an edge of theconductor and wherein the at least one second magnetic field sensingelement is configured to generate a second magnetic field signalindicative of a second distance between the at least one second magneticfield sensing element and the edge of the conductor, wherein the firstdistance and the second distance are different distances; and a circuitresponsive to the first magnetic field signal and to the second magneticfield signal and configured to generate a difference signal indicativeof a difference between the first magnetic field signal and the secondmagnetic field signal, wherein the difference is indicative of thecurrent carried by the conductor.
 2. The current sensor of claim 1,wherein the lead frame further comprises a die attach paddle and the oneor more substrates are attached to the die attach paddle.
 3. The currentsensor of claim 2, wherein the one or more substrates have a firstsurface attached to the die attach paddle and a second, opposingsurface, and wherein the plurality of magnetic field sensing elementsare supported by the second surface of the one or more substrates. 4.The current sensor of claim 1, wherein the one or more substrates have afirst surface attached to one or more of the plurality of leads, and asecond, opposing surface distal from the lead frame, and wherein theplurality of magnetic field sensing elements are supported by the firstsurface of the one or more substrates.
 5. The current sensor of claim 1,wherein the at least one first magnetic field sensing element isvertically aligned with the external conductor and the at least onesecond magnetic field sensing element is not vertically aligned with theexternal conductor.
 6. The current sensor of claim 2, wherein the dieattach paddle comprises one or more slits, slots or apertures.
 7. Thecurrent sensor of claim 2, wherein the plurality of leads are disposedat a first height with respect to the external conductor and the dieattach paddle is disposed at a second height with respect to theexternal conductor, wherein the first height is different from andgreater than the second height.
 8. The current sensor of claim 2,further comprising a mold material enclosing the one or more substratesand a portion of the lead frame including the die attach paddle, andwherein a first plurality of the leads extend from a first side of themold material and a second plurality of the leads extend from a second,opposite side of the mold material, and wherein the die attach paddle isattached to one or more of the first plurality of the leads and isspaced from the second plurality of leads.
 9. The current sensor ofclaim 1, wherein the plurality of magnetic field sensing elementscomprises at least one of a Hall effect element or a magnetoresistanceelement.
 10. The current sensor of claim 9, wherein themagnetoresistance element comprises at least one of Indium Antimonide(InSb), a giant magnetoresistance (GMR) element, an anisotropicmagnetoresistance (AMR) element, a tunneling magnetoresistance (TMR)element or a magnetic tunnel junction (MTJ) element.
 11. A currentsensor for sensing a magnetic field generated by a current through anexternal conductor comprising: a lead frame having a first surface and asecond, opposing surface, a die attach paddle, a first plurality ofleads and a second plurality of leads, the die attach paddle havingfirst side adjacent to the first plurality of leads and second, opposingside adjacent to the second plurality of leads, wherein the first sideof the die attach paddle is attached to at least one of the firstplurality of leads and wherein the second side of the die attach paddleis spaced apart and electrically isolated from the second plurality ofleads; one or more substrates attached to the die attach paddle; and aplurality of magnetic field sensing elements supported by the one ormore substrates, wherein at least one first magnetic field sensingelement of the plurality of magnetic field sensing elements is spacedfrom at least one second magnetic field sensing element of the pluralityof magnetic field sensing elements such that the at least one firstmagnetic field sensing element is closer to the first side of the dieattach paddle than to the second side of the die attach paddle and theat least one second magnetic field sensing element is closer to thesecond side of the die attach paddle than to the first side of the dieattach paddle.
 12. The current sensor of claim 11, wherein the one ormore substrates have a first surface attached to the die attach paddleand a second, opposing surface, and wherein the plurality of magneticfield sensing elements are supported by the second surface of the one ormore substrates.
 13. The current sensor of claim 11, wherein the atleast one first magnetic field sensing element is configured to generatea first magnetic field signal indicative of a distance between the atleast one first magnetic field sensing element and the conductor andwherein the at least one second magnetic field sensing element isconfigured to generate a second magnetic field signal indicative of adistance between the at least one second magnetic field sensing elementand the conductor, and wherein the current sensor further comprises acircuit responsive to the first magnetic field signal and to the secondmagnetic field signal and configured to generate a difference signalindicative of a difference between the first magnetic field signal andthe second magnetic field signal, wherein the difference is indicativeof the current carried by the conductor.
 14. The current sensor of claim11, wherein the at least one first magnetic field sensing element isvertically aligned with the conductor and the at least one secondmagnetic field sensing element is not vertically aligned with theconductor.
 15. The current sensor of claim 11, wherein the die attachpaddle comprises one or more slits, slots or apertures.
 16. The currentsensor of claim 11, wherein the first and second plurality of leads aredisposed at a first height with respect to the conductor and the dieattach paddle is disposed at a second height with respect to theconductor, wherein the first height is different from and greater thanthe second height.
 17. The current sensor of claim 11, furthercomprising a mold material enclosing the one or more substrates and aportion of the lead frame including the die attach paddle, and whereinthe first plurality of the leads extends from a first side of moldmaterial and the second plurality of the leads extends from a second,opposite side of the mold material.
 18. The current sensor of claim 11,wherein the plurality of magnetic field sensing elements comprises atleast one of a Hall effect element or a magnetoresistance element. 19.The current sensor of claim 18, wherein the magnetoresistance elementcomprises at least one of Indium Antimonide (InSb), a giantmagnetoresistance (GMR) element, an anisotropic magnetoresistance (AMR)element, a tunneling magnetoresistance (TMR) element or a magnetictunnel junction (MTJ) element.
 20. A method for sensing a magnetic fieldgenerated by a current through an external conductor, the methodcomprising: providing a lead frame having a first surface and a second,opposing surface, the lead frame comprising a die attach paddle and aplurality of leads, wherein one or more substrates are attached to thedie attach paddle; providing a current sensor comprising a plurality ofmagnetic field sensing elements supported by a surface of the one ormore substrates, wherein at least one first magnetic field sensingelement of the plurality of magnetic field sensing elements is spacedfrom at least one second magnetic field sensing element of the pluralityof magnetic field sensing elements; sensing the magnetic field by the atleast one first magnetic field sensing element and the at least onesecond magnetic field sensing element, wherein the at least one firstmagnetic field sensing element and the at least one second magneticfield sensing element are orientated to sense the magnetic field in thesame direction; generating a first magnetic field signal indicative of afirst distance between the at least one first magnetic field sensingelement and an edge of the conductor; generating a second magnetic fieldsignal indicative of a second distance between the at least one secondmagnetic field sensing element and the edge of the conductor, whereinthe second distance is different than the first distance; and generatinga difference signal indicative of a difference between the firstmagnetic field signal and the second magnetic field signal, wherein thedifference is indicative of the current carried by the conductor. 21.The method of claim 20, further comprising positioning the at least onefirst magnetic field sensing element such that it is vertically alignedwith the conductor and positioning the at least one second magneticfield sensing element such that it is not vertically aligned with theconductor.
 22. The method of claim 20, further comprising forming one ormore slits, slots or apertures in the die attach paddle.
 23. The methodof claim 20, further comprising disposing the plurality of leads at afirst height with respect to the conductor and disposing the die attachpaddle at a second height with respect to the conductor, wherein thefirst height is different from and greater than the second height. 24.The method of claim 20, further comprising enclosing the one or moresubstrates and a portion of the lead frame including the die attachpaddle in a mold material, and wherein a first plurality of the leadsextends from a first side of mold material and a second plurality of theleads extends from a second, opposite side of the mold material, andwherein the die attach paddle is attached to one or more of the firstplurality of the leads and is spaced from the second plurality of leads.25. The method of claim 20, wherein the plurality of magnetic fieldsensing elements comprises at least one of a Hall effect element or amagnetoresistance element.
 26. The method of claim 25, wherein themagnetoresistance element comprises at least one of Indium Antimonide(InSb), a giant magnetoresistance (GMR) element, an anisotropicmagnetoresistance (AMR) element, a tunneling magnetoresistance (TMR)element or a magnetic tunnel junction (MTJ) element.
 27. A currentsensor for sensing a magnetic field generated by a current through anexternal conductor, the magnetic field having a direction associatedwith a direction of the current through the conductor, comprising: firstmeans for sensing the magnetic field generated by the current togenerate a first magnetic field signal indicative of a first distancebetween the first magnetic field sensing means and an edge of theconductor; second means for sensing the magnetic field generated by thecurrent to generate a second magnetic field signal indicative of asecond distance between the second magnetic field sensing means and theedge of the conductor, wherein the second distance is different than thefirst distance; means for supporting the first magnetic field sensingmeans and the second magnetic field sensing means in a spacedrelationship, but with both the first and second magnetic field sensingmeans oriented to sense the magnetic field in the same direction; andmeans for determining a difference between the first magnetic fieldsignal and the second magnetic field signal, wherein the difference isindicative of the current through the conductor.
 28. The current sensorof claim 27, wherein the first magnetic field sensing means isvertically aligned with the external conductor and the second magneticfield sensing means is not vertically aligned with the externalconductor.